How OTN+PTN technology deeply supports local network construction?

OTN and PTN, as emerging technologies, will play a pivotal role
in next-generation optical transport networks.
From a technical point of view, the PTN+OTN joint networking model has been completely feasible, but limited to the short development time of the technology itself, the rapid development of technology, many unknown problems need to be further studied and discussed, such as how to reasonably and effectively select and plan the network in the metro network and local network, and how to effectively carry out joint networking, which has become a topic
of great concern in the current industry.

A new model of OTN+PTN joint networking

Whether it is from the perspective of long-distance transmission of services or the rapid growth of future IP services, it is necessary
to adopt the OTN+PTN joint networking mode.
With its powerful IP service access, aggregation and flexible scheduling capabilities, the OTN+PTN joint networking mode is conducive to promoting the evolution of metro transport networks to a unified and converged flat network, and is the best choice
for building next-generation transmission networks.

1.
OTN technology advantages

The advantage of OTN is that it solves the problem of ultra-long distance and ultra-large bandwidth transmission of IP services, and can provide transmission channels for a large number of large particles such as 2.
5Gbit/s, 10Gbit/s, and even 40Gbit/s, which is difficult to achieve with PTN
.
However, the bandwidth allocation of OTN is also rigid, and the bandwidth utilization rate is not high, which makes it difficult to process
smaller grain services.

2.
PTN technology advantages

The beauty of PTN technology is that it perfectly combines data technology and transmission technology, large-capacity packet switching/label switching technology from data, QoS technology, OAM management from transmission, 50ms protection and synchronization, which can maximize the technical advantages of operators' infrastructure network infrastructure, enhance the flexibility of rapid deployment of new applications in the future and reduce costs
.
The advantages of PTN are reflected in the flexible access of small-particle IP services and the aggregation and convergence of services, but it is not good at transmitting
a large number of large-particle services.
Therefore, the joint networking of the two complements each other, providing ultra-long-distance, ultra-large capacity, and flexible scheduling networks
.

Example analysis of OTN+PTN networking solution

As a large-capacity networking technology with photoelectric joint scheduling, OTN realizes sub-wavelength-based scheduling, such as GE, 2.
5Gbit/s, and 10 Gbit/s particles.
Optical layer scheduling is mainly based on 10 Gbit/s or 40 Gbit/s wavelengths, which is mainly located in the backbone/core layer
of the network.
PTN, similar to MSTP, is mostly used in the aggregation/access layer
of the network.
In the existing network, OTN is often used at the core backbone layer and PTN networking is used at the aggregation layer and below, making full use of OTN to dispatch uplink services to PTN-owned service landing sites
.

In the joint networking mode, OTN is not only a means of bearing, but also scheduling between the GE/10GE service connected to the backbone node and the cross-landing equipment to which it belongs, and the number of uplink GE/10GE channels can be configured according to the total number of services actually connected in the PTN, thereby greatly simplifying the network formation between the backbone node and the core node, avoiding the PTN independent networking mode.
The service capacity upgrade of a node causes all node devices on the loop to be upgraded, which greatly saves network investment
.

Issues that should be paid attention to in OTN+PTN joint networking

As new technologies, OTN and PTN do not have long-term large-scale networking experience, and the two influence and complement each other in actual networking
.
Therefore, the following issues
should be considered when using the OTN+PTN joint networking mode.

1.
Device interoperability

Both PTN and OTN are emerging technologies, and OTN inherits the large-capacity transmission function of DWDM and introduces flexible scheduling functions
based on wavelengths and sub-wavelengths.
Its biggest feature is that it adopts a fully open system architecture, and the service it carries is the relationship between the customer layer and the service layer, which is a transparent transmission platform, providing a transmission channel for the PTN of the aggregation layer and the access layer, and the relationship between the two, such as the service layer and the customer layer, is independent of each other, similar to the WDM and SDH network relationships
that have been widely deployed.
OTN carries PTN, just as
WDM carries SDH.

2.
Precise time synchronization

Time synchronization is a new requirement put forward by the 3G mobile standard, there is currently no accurate time synchronization network, so when building a transmission network, special attention should be paid to the problem
of accurate time synchronization.
From the perspective of the technical system of terrestrial transmission time synchronization, accurate time synchronization
is mainly completed through the IEEE 1588v2 protocol.
Due to the joint networking mode of OTN+PTN, OTN devices are deployed in the backbone core layer of the network, PTN devices are deployed in the aggregation and access layers, and the time source is first deployed on the RNC side of the local network core equipment room, and the RNC first transmits the time synchronization information to the core layer PTN, and the core layer PTN is then transmitted to the core layer OTN devices, and the OTN devices are transmitted to the PTN devices of other layers in turn for network-wide accurate time synchronization
.

At present, the PTN bearer 1588v2 protocol has become a basic technology
of PTN.
If the OTN+PTN joint networking mode is adopted, OTN is required to support the relevant accurate time transmission function
.

3.
Protection issues

Network security is above all else, regardless of the use of OTN and PTN networking, it is necessary to consider the protection of the network uniformly
.
OTN devices are deployed at the backbone core layer of the network, and PTN devices are deployed in the aggregation and access layers, requiring a large number of service intercommunication and scheduling between each layer, and end-to-end or segmented protection
of services.

4.
Interface consistency

In metro networks and local networks, data services often occupy the mainstream of services, especially GE and 10GE services occupy an absolutely dominant position
。 When using OTN+PTN joint networking mode, there are a large number of PTN and OTN client-side interfaces through GE, 10GE interface for business docking, should pay attention to the consistency of the interface in the networking, taking 10GE signal as an example, ITU-T in G.
709 and G.
sup43 defines several 10GE LAN signals in OTN network mapping methods, including standard GFP-F mode G.
sup43 6.
2, ODU2e mode G.
709 17.
1.
4 and extended GFP-F/OPU2 mode G.
709 17.
3.
1, packaging and mapping signal consistency issues
should be maintained.

5.
Network management platform

From the perspective of network management, the PTN and OTN of mainstream manufacturers in the industry can realize the common network management platform to facilitate network maintenance
.
In the joint networking mode of PTN and OTN, OTN is often positioned at the core layer, PTN is positioned at the aggregation and access layers, and a large number of services are required and scheduled between various layers, so higher requirements
are put forward for both service provisioning and the maintenance needs of network management itself.

6.
Network maintenance

At present, the reality of metro networks and local networks is that there are many equipment levels and complex networking, which brings great difficulty
to the fault location of the network.
When using OTN+PTN joint networking, PTN and OTN technology have inherited SDH's powerful hierarchical OAM management mechanism, service encapsulation has corresponding rich overhead for monitoring, PTN OAM includes customer layer OAM, channel layer OAM, channel layer OAM and segment layer OAM, OTN supports 6 levels of TCM, SM, PM, etc.
, each layer provides fault and performance OAM to achieve real-time and accurate fault location functions at different levels
。